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					Nuclear Chemistry




                    1
 Facts About the Nucleus

Very small volume compared to
 volume of atom

Essentially entire mass of atom
 Very dense
Facts About the Nucleus
(continued)
Composed of protons and
 neutrons that are tightly held
 together
  Nucleons

Every atom of an element has
 the same number of protons
  Atomic Number (Z)
Facts About the Nucleus
(continued)
Isotopes are atoms of the same
 elements that have different
 masses
 Different numbers of neutrons
 Mass Number (A)
 = number of protons + neutrons
Facts About the Nucleus
(continued)

The nucleus of a specific isotope
 is called a nuclide
  less than 10% of the known
   nuclides are nonradioactive,
   most are radioactive
   (radionuclides)
Nuclides

Each nuclide is
 identified by a
 symbol where:
                     A
X = element symbol
A = mass number      Z   X
Z = atomic number
Nuclear Reactions
with respect to other changes
Energy drives all reactions, physical, chemical, biological, and nuclear.
Physical reactions change states of material among solids, liquids,
gases, solutions. Molecules of substances remain the same.
Chemical reactions change the molecules of substances, but identities
of elements remain the same.
Biological reactions are combinations of chemical and physical
reactions.
Nuclear reactions change the atomic nuclei and thus the identities of
nuclides. They are accomplished by bombardment using subatomic
particles or photons.
Nuclear Reactions
  changing the hearts of atoms
Nuclear reactions, usually induced by subatomic particles a, change
the energy states or number of nucleons of nuclides.


After bombarded by a,                                       b
                                        A (a,b) B
the nuclide A emits a
subatomic particle b,          a
and changes into B.
    a+A B+b
                                           A            B
or written as A (a,b) B
Nuclear Reactions
 Radioactive decay – a process by which the nucleus
  of a nuclide emits radioactive particles

 Artificial Nuclear Transformation – the changing of
  one element into another by bombarding it with a
  nuclide

 Nuclear Fission – the process of using a neutron to
  split a heavy nucleus into two smaller nuclei

 Nuclear Fusion – the process of combining two light
  nuclei
Subatomic Particles for and from
Nuclear Reactions

Subatomic particles used to bombard or emitted in nuclear reactions:
gamma ray (photon)                    deuterons
                                 0γ                     2
                                                        1   D
electrons                             alpha particles
                             0                           4
                            1   e                           He
                                                         2

protons                               beta particles
            1
            1   p   1
                    1   H
                                                          0
                                                         1   
neutrons                              atomic nuclei
                            1                           A
                            0   n                       Z    X
Nuclear equations rules

Sum of reactant mass numbers = sum of
 product mass numbers
Sum of reactant atomic numbers = sum
 of product atomic numbers
“emitted” particles are on product side
“bombarding” or “captured” particles are
 on reactant side
  Radioactive Decay


Radioactive nuclei spontaneously
 decompose into smaller nuclei
 We say that radioactive nuclei are
  unstable
 Decomposing involves the nuclide
  emitting a particle and/or energy
Radiation

Radiation comes from the nucleus of an
 atom.
Unstable nucleus emits a particle or energy

                         alpha
                         beta

                         gamma
                         4
alpha decay              2    He

an  particle contains 2 protons and
 2 neutrons
  helium nucleus
                Alpha Decay
          A Z          A–4
          P               DZ–2


                                   4He2
Alpha decay (continued)



222
 88   Ra  He 
            4
            2
                    218
                     86   Rn
Beta decay

a  particle is like an electron
 moving much faster
 found in the nucleus

in beta decay a neutron changes into
 a proton
Beta decay (continued)



234
 90 Th       0
             1   e   234
                        91   Pa
gamma emission
Gamma () rays are high energy
 photons

Gamma emission occurs when
 the nucleus rearranges

No loss of particles from the
 nucleus
gamma emission
(continued)
No change in the composition of the
 nucleus
 Same atomic number and mass
   number

Generally occurs whenever the
 nucleus undergoes some other type
 of decay
 positron emission


positron has a charge of +1 and
 negligible mass
 anti-electron

positrons appear to result from a
 proton changing into a neutron
Positron emission
(continued)




  22
  11   Na  e  Ne
             0
            1
                    22
                    10
electron capture

occurs when an inner orbital
 electron is pulled into the nucleus

no particle emission, but atom
 changes
 –same result as positron
   emission
Electron capture
(continued)




200
 80
    Hg  1e 
           0       200
                   79
                      Au
Artificial Nuclear
Transformation
Nuclear transformation involves
 changing one element into another
 by bombarding it with small nuclei,
 protons or neutrons

reaction done in a particle
 accelerator
Artificial Nuclear
Transformation (continued)

man-made transuranium
 elements

 238
  92   U C4 n 
         12
          6
                1
                0
                     246
                      98   Cf
Other Nuclear Changes


a few nuclei are so unstable,
 that if their nucleus is hit just
 right by a neutron, the large
 nucleus splits into two smaller
 nuclei - this is called fission
Fission




  U  n Ba  Kr 3 n
235
 92
      1
      0
          142
           56
                91
                36
                     1
                     0
Other Nuclear Changes
(continued)

small nuclei can be accelerated
 to such a degree that they
 overcome their charge repulsion
 and are smashed together to
 make a larger nucleus - this is
 called fusion
Fusion



 2
 1   H  H  He
         2
         1
             4
             2
Other Nuclear Changes
(continued)

both fission and fusion
 release enormous amounts of
 energy
Learning Check NR1

 Write the nuclear equation for the beta
 emitter Co-60.
Solution NR1

Write the nuclear equation for the
Beta emitter Co-60.

     60Co                60Ni   +     0e

      27                28           -1
Learning Check NR2

 What radioactive isotope is produced
 in the following bombardment of
 boron?

 10B   +   4He           ? +    1n

 5         2                    0
Solution NR2

 What radioactive isotope is produced
 in the following bombardment of
 boron?

 10B   +   4He         13N       +   1n

 5         2           7             0

                  nitrogen
                  radioisotope
Day 2 – Radioactivity Effects
and Applications
Detecting Radioactivity

To detect something, you need to
 identify something it does

radioactive rays cause air to
 become ionized
Detection (continued)
Geiger-Müller Counter works by
 counting electrons generated when
 Ar gas atoms are ionized by
 radioactive rays
Detecting Radioactivity
(continued)
radioactive rays cause certain
 chemicals to give off a flash of
 light when they strike the
 chemical

a scintillation counter is able to
 count the number of flashes per
 minute
         Scintillation Counters
           The Key Components of a Typical Scintillation Counter

           Na(Tl)I
           crystal
X- or            Photo-
 rays           cathode
                                                          High voltage
                                                          supplier and
                                                          multi-channel
                                                          analyzer /
                                                          computer
                                                          system
    Thin Al                Photomultiply tube
    window



                            Photons cause the emission of a
                            short flash in the Na(Tl)I crystal.
                            The flashes cause the photo-cathode
                            to emit electrons.
Scintillation
Detector
Detecting Radioactivity
(continued)
radioactive rays cause chemical
 changes in some materials
Photographic film is able to
 “record” its interactions with
 radioactive particles
Photographic Emulsions and
Films

Sensitized silver bromide grains of emulsion develope
into blackened grains. Plates and films are 2-D
detectors.
Roentegen used photographic plates to record X-ray image.
Photographic plates helped Beckerel to discover radioactivity.
Films are routinely used to record X-ray images in medicine but
lately digital images are replacing films.
Stacks of films record 3-dimensional tracks of particles.
Photographic plates and films are routinely used to record
images made by electrons.
  Half-Life


Not all radionuclides in a sample
 decay at once (random process)

The length of time it takes one-half
 the radionuclides to decay is called
 the half-life
Half-life (continued)

Even though the number of
 radionuclides changes, the length
 of time it takes for half of them to
 decay does not

  the half-life of a radionuclide is
   constant
Half-life (continued)

Each radionuclide has its own,
 unique half-life
The radionuclide with the shortest
 half-life will have the greater number
 of decays per minute (For samples
 of equal numbers of radioactive
 atoms)
Half-Life of a Radioisotope

  The time for the radiation level to fall
  (decay) to one-half its initial value

                          decay curve

    initial
                1
              half-life
                           2      3
    8 mg 4 mg             2 mg    1 mg
Examples of Half-Life

Isotope    Half life
C-15       2.4 sec
Ra-224     3.6 days
Ra-223     12 days
I-125      60 days
C-14       5700 years
U-235      710 000 000 years
Learning Check NR3

 The half life of I-123 is 13 hr. How
 much of a 64 mg sample of I-123 is left
 after 26 hours?
Solution NR3

 t1/2             =   13 hrs
 26 hours         =   2 x t1/2
 Amount initial   =   64mg
 Amount remaining = 64 mg x ½ x ½
                  = 16 mg
Ionizing Radiation
radioactivity measurements

High energy particles and photons that ionise atoms and molecules
along their tracks in a medium are called ionizing radiation. For
example, , , , cosmic rays and X-rays are ionizing radiation.
Most radioactive measurement are based on their ionizing effect.
Ionizing radiation causes illness such as cancer and death.
Radiation effect is a health and safety concern.
Ionizing radiation can also be used in industry for various purposes.
Light and microwaves that do not ionize atoms and molecules are
called non-ionizing radiation.
   Interaction of Heavy Charged Particles with
   Matter

                             Sketch of Alpha Particle Paths in a Medium


Fast moving protons, 4He,
and other nuclei are
heavy charged particles.
                                  source
Coulomb force dominates
charge interaction.                  Shield
They ionize and excite
(give energy to) molecules
on their path.
   Scattering of Electrons in a Medium
An Imaginary Path of a  particle in
           a Medium
                                       Fast moving electrons are
                                       light charged particles.
                                       They travel at higher speed.,
                                       but scattered easily by
                                       electrons.


                                              source


                                                  Shield
Factors that Determine
Biological Effects of Radiation

The more energy the radiation has
 the larger its effect can be
The better the ionizing radiation
 penetrates human tissue, the deeper
 effect it can have
  Gamma >> Beta > Alpha
Factors that Determine
Biological Effects of Radiation
(continued)
Factors that Determine
Biological Effects of Radiation (continued)


The more ionizing the radiation
 (based on mass and charge), the
 greater effect the radiation has
  Alpha > Beta > Gamma
Radiation Protection


Shielding
    alpha – paper, clothing
    beta – lab coat, gloves
    gamma- lead, thick concrete
Limit time exposed
Keep distance from source
Factors that Determine
Biological Effects of Radiation
(continued)
Factors that Determine
Biological Effects of Radiation (continued)

  The radioactive half-life of the
    radionuclide
  ° The biological half-life of the element
  ±The physical state of the radioactive
    material
Factors that Determine
Biological Effects of Radiation (continued)



  The amount of danger to humans of
   radiation is measured in the unit
   rems
Somatic Damage

Somatic Damage is damage which
 has an impact on the organism
  Sickness or Death
May be seen immediately or in the
 future
  Depends on the amount of
   exposure
  Future effects include cancer
Genetic Damage

Genetic Damage occurs when the
 radiation causes damage to
 reproductive cells or organs
 resulting in damage to future
 offspring
 Nuclear Technologies
X-rays give penetrating vision to inner structures under cover.
X-rays and computers give 4-D images of wholes.
X-ray diffraction enables us to determine crystal and molecular
structures, including those of DNA.
Ionizing radiation effects and sterilization empower industries.
Radioactive decay kinetics enables dating.
Radioactivity causes and cures illness.
Nuclear reactions led to nuclide and element synthesis.
Pair productions give positrons and electrons for accelerators.
Positron-electron annihilations tell stories of organ functions.
Nuclear reactions activate atoms and nuclides in microscopic samples.
Fission and fusion energy for war and peace.
                     Radiology
Radiology is a scientific discipline dealing with medical imaging using
ionizing radiation, radionuclides, nuclear magnetic resonance, and
ultrasound. The following procedures are currently widely available:

    Central Nervous System: Brain,Spine
    Cardiovascular System: heart, blood vessels
    Musculoskeletal System: bone, muscles, and joints
    Digestive, Urinary, and Respiratory System: intestines,
    kidneys, liver, stomach, lungs
    Reproductive System and Mammography: male and
    female reproductive organs and breasts
X-ray Tubes
-X-ray tubes for industry and
sciences.
- Non-destructive testing X-ray
Inspection and X-ray Baggage
Inspection and Thickness
Gauging.

--There are hundreds of X-ray
tubes for medical applications.

Image from prd004-5 of Varian.
  X-ray Imaging

Absorption of X-ray and gamma-ray by different
material for image: today, 2-dimensional solid state
detectors are used in place of films for X-ray and
gamma-ray imaging as shown in this image by Varian
 Mammography and CT Scan
 X-rays provide the sharpest images of the breast's inner structure.
 Mammogram detects small tumors and changes in the breast tissues.
Computed tomography (CT), scanner takes images by rotating an x-
ray tube around the body while measuring the constantly changing
absorption of the x-ray beam by different tissues in your body.

The sensitive scanner provides small
differences in absorption of the beam by
various tissues. The information is fed into
a computer which reconstruct images of
thin cross sections of the body.
Impact of X-ray Diffraction
 Using X-ray diffraction, nearly all structure
 of compounds artificially made or isolated
 from nature have been determined,
 including structures of semiconductors,
 DNA molecules, and proteins. Structure
 data banks serve science, technologies,
 and medicine.
X-ray Diffraction Results

 X-ray diffraction pattern of a single crystal
showing positive image of X-ray beams.
Intensities of these beams allows us to
determine molecular and crystal structures.
Various data banks of structures are now
available for research and development.
Medical Uses of Radioisotopes,
Diagnosis

Diagnosis (radiotracers)
  Usually gamma emitters
  Little interaction with tissue
Therapy
  Alpha or beta emitters (interact with tissue)
  May also emit gamma (detect outside body)
Medical Uses of Radioisotopes,
Diagnosis

radiotracers
 certain organs absorb most or all of a
   particular element
 can measure the amount absorbed by
   using tagged isotopes of the element
   and a Geiger counter
Radionuclide in Medicine

 Radionuclides are used in imaging for diagnosis and treatment.
 Nuclides specifically accumulate in organs (based on chemical
 properties) for image and diagnoses.

 Radionuclide therapy selectively deliver radiation doses in
 target tissues.
History of Nuclear Midicine
1895 – discovery of X-rays
1934 – discovery of artificial radioactivity
1937 – artificial radioactivity was used to treat leukemia at UC Berkeley
1946 – use of radioactive iodine cured thyroid cancer
1948 – Abbott Laboratories began distribution of radioistopes
1950s – radioactive iodine was widely used to diagnose and treat thyroid
1953 – Gordon Brownell and H.H. Sweet built a positron detector
1971 - The American Medical Association officially recognized nuclear
medicine as a medical speciality
About Nuclear Medicine
There are nearly 100 different nuclear medicine imaging
procedures available today.
Nuclear medicine uniquely provides information about
both the function and structure of virtually every major
organ system within the body.
There are approximately 2,700 full-time equivalent nuclear
medicine physicians and 14,000 certified nuclear medicine
technologists in the U.S.
Nuclear Medicine
Applications
Neurologic: Diagnose stroke, alzheimer’s disease, localize seizure foci, evaluate
post concussion

Oncologic: Tumor localization, staging, and response to treatments
Orthopedic: Evaluate bone, arthritic changes, and extent of tumors
Renal: Detect urinary tract obstruction and measure renal functions
Cardiac: Diagnose coronary artery, measure effectiveness of bypass surgery,
identify patients of high risk heart attack, and diagnose heart attacks

Pulmonary: Measure lung functions
Other: Diagnose and Treat Hyperthyroidism (Grave's Disease)
Irradiation Sterilization
 Irradiation by ionizing radiation kills bacteria and cells. This effect
 has been applied for the following areas:
 sterilize medical equipment
 sterilize consumer products such as baby bottle, pacifiers, hygiene
 products, hair brush, sewage
 sterilize common home and industry products
 food preservation
Irradiation for Food
Processing
Soon after discovery, X-rays were used to kill insects and their eggs.
After WWII, spent fuel rod were used to sterilize food, but soon, 60Co
was found easier to use in th 1950s.
The US army played a key role in R & D of food processing, and
soon other countries followed.
In 1958, USSR granted irradiation of potatoes for sprout inhibition.
Canada granted irradiation of potatoes, onions, wheat, dry spices.
However, food processing has many other problems such as
regulation, labelling, marketing and public acceptance to deal with.
Object dating

archeological (once living materials)
  compare the amount of C-14 to C-12
  C-14 radioactive with half-life = 5730yrs.
  while living, C-14/C-12 fairly constant
Object dating (continued)
 CO2 in air ultimate source of all C in
  body
 atmospheric chemistry keeps
  producing C-14 at the same rate it
  decays
 Upon death, C-14/C-12 ratio decreases
 limit up to 50,000 years
Radiocarbon Formation
and Exchange
 Cosmic
   rays
          n          14N         proton

                           14C
          14CO
                 2          CO2
Physical Data of                          14C

Beta energy              156keV (maximum), 49 keV (ave)
Half life                5730 y
Biological half life     12 d
Effective half life      12 d (unbound)
                         40 d (bound)
Max. beta range in air 24 cm
Max. beta range in water 0.28 mm
Best used to date objects less than 50,000 years old.
 Object Dating


mineral (geological)
 compare the amount of U-238 to
  Pb-206
 compare amount of K-40 to Ar-
  40
Radiopotassium                           40K      Dating
Radiopotassium 40K decays to stable 40Ar. Thus, by measuring relative
ratio of 40K and 40Ar in rocks enable us to determine the age of rocks
since its formation.The half life of 40K is 1.25e9 y.
 Fissionable Material

fissionable isotopes include U-235, Pu-
 239, and Pu-240

natural uranium is less than 1% U-235
 rest mostly U-238
 not enough U-235 to sustain chain
  reaction
Fissionable Material
(continued)
fission produces about 2.1 x 1013
 J/mol of U-235
  26 million times the energy of
   burning 1 mole CH4

to produce fissionable uranium the
 natural uranium must be enriched in
 U-235
Fission Chain Reaction


a chain reaction occurs when
 a reactant is also a product
 in the fission process it is the
   neutrons
 only need a small amount of
   neutrons to keep the chain
   going
Fission Chain Reaction
(continued)

many of the neutrons produced
 in the fission are either ejected
 from the uranium before they hit
 another U-235 or are absorbed by
 the surrounding U-238
Fission Chain Reaction
(continued)

minimum amount of fissionable
 isotope needed to sustain the
 chain reaction is called the
 critical mass
Nuclear fission
Nuclear fission
  Nuclear Power Plants

use fission of U-235 or Pu-240 to
 make heat

the fission reaction takes place in
 the reactor core
Nuclear Power Plants
Nuclear Power Plants
(continued)

heat picked up by coolant and
 transferred to the boiler
in the boiler the heat boils water,
 changes it to steam, which turns
 a turbine, which generates
 electricity
  Nuclear Power Plants -
  Core

the fissionable material is stored in
 long tubes arranged in a matrix
 called fuel rods
  subcritical
Nuclear Power Plants -
Core (continued)

between the fuel rods are
 control rods made of neutron
 absorbing material
 B and/or Cd
 neutrons needed to sustain the
  chain reaction
Nuclear Power Plants -
Core (continued)

the rods are placed in a material
 used to slow down the ejected
 neutrons called a moderator
 allows chain reaction to occur
   below critical mass
Reactor core (fuel):
   enriched or natural U, 239Pu
Moderators
   graphite,
   H2O, D2O                                 Key Components
   He (100 Atm and 1273 K)
   Be (high temperature liquid metal).            of Nuclear
   Na (773 to 873 K for breeder reactor)
   BeF2 + ZrF4 ( for GCR)                          Reactors
Control rods
   Cadmium, Boron, Carbon, Cobalt, Silver,
   Hafnium, and Gadolinium,  c =255 kb for 157Gd Monitoring devices
   Neutron and radioactivity detectors, T, etc
Energy transfer system
   Moderator or liquid
              Reactor accidents
An accident is a series of undesirable events that took
place due to accumulated causes.
Nuclear accidents attract more attention due to release of
radioactive nuclides.
Radioactivity causes fear, because most people know
little about it.
Many nuclear accidents have happened.
              TMI-2 Reactor accidents

March 28, 1979, two pumps failed to supply feed water
steam generator.
Valve of auxiliary pump was closed by error and auxiliary
pump failed to operate.
Pressure increased and relieve valves opened.
Relieve valves failed to close resulting in a loss of coolant.
Zircaloy-4 oxidized by water, producing a large volume of
hydrogen gas.
Core overheated resulting in meltdown
The TMI-2 Reactor Design
      The TMI-2 Core After the Accident
                                                                             Four years later,
                                                                             photo image of
                                                                             TMI–2 core shows
                                                                             damage to its
                                                                             uranium fuel rods
                                                                             more extensive
                                                                             than originally
                                                                             thought just after he
                                                                             accident.
                                                                             Core meltdown
                                                                             shows the
                                                                             temperature
                                                                             reached 5000 K.

http://washingtonpost.com/wp-srv/national/longterm/tmi/gallery/photo10.htm
Fission Products in the Core After the Accident

 Long-life Fission Products in the Core after TMI-2 Accident

 Isotope Activity /Ci Half-life Amount*
 85K      9.7104       10.7 y         4.71013
 90Sr     7.5105       28.8 y         9.81014
 129I     2.210–3      1.6107 y 1.61012
 131I     7.0107       8.04 d         7.01013
 133Xe    1.5108       5.25 d         9.81013
 137Cs    8.4105       30.2 y         1.11015
  * Amount = Activity  half-life (s)/0.693
                 The Chernobyl Accident
RBMK graphite-moderated, channel-tube-cooled reactors. Reactor 4
in Chernobyl had been in operation for 3 years prior to the accident.
April 26, 1986, Reactor 4 at Chernobyl was scheduled for a safety test
to see if residual power is sufficient to operate the reactor safely in
case of a sudden power failure.
Operators turned off cooling system and powered down. When power
from the reactor failed to operate the reactor safely, they used power
from the grid without notifying grid controller. Radioactivity of fission
products overheat the core. When they turned up power with cooling
system off, the core fragmented and exploded destroying the building.
Radioactivity (fallout) spread to north Europe.
The Soviet RBMK Reactor Design
                             The Soviet
                             RBMK reactor
                             has individual
                             fuel channels,
                             using ordinary
                             water as
                             coolant and
                             graphite as
                             moderator. It
                             evolved from
                             reactors
                             designed for
                             239Pu

                             production.
Power Nuclear Reactors in the World




      nucleartourist.com/world/wwide1.htm
                          Major work sites:
  The First Fission       Oak Ridge 59,000-acre
  Bomb Explosion          Hanford Engineer Work 450,000-acre
                          Project Y (Los Alamos Laboratory)
                          Chicago, Berkley, Montreal, New York

July 16, 1945, a
plutonium (Fat Man)
bomb was tested in
Journey of Death. Two
hemispheres of 239Pu
were forced together to
reach criticality. The
bomb was attached to a
30-meter steel tower,
which disappeared after
the explosion.
          Fission Energy For War
At 8:15 am August 6, 1945, Little Boy (235U) was dropped
on Hiroshima by a modified B-29 bomber.

On the 9th, a 239Pu-fuelled bomb exploded over Nagasaki


                               Destruction by atomic bomb
                                Light and energy (heat)
                                Shock wave
                                Secondary fire
                                Radioactive fission products
                                  in the fallout
                    The Implosion Arrangement

                   Ignition                    Chemical
                    points                     explosive
Reducing
Critical                           239
                                         Pu
Masses by
Implosion

            Fission material is surrounded by chemical explosive
            which is ignited at many points simultaneously. The
            explosion forces pieces of 239Pu together and even
            reduces the volume to reduce the critical mass.
  Producing Bomb Materials

Separate 235U (0.7%) from natural     235
                                            U
uranium:                              239
                                            Pu
      gas diffusion of UF6
      centrifuge of UF6 gas
      thermal diffusion of UF6 gas
      electromagnetic separation

Production of 239Pu by the reaction
      238U(n, 2)239Pu
Bomb Material:     Separating 235U by gas Diffusion
                                          One diffusion unit
                                         and
                                         the diffusion plant 




    The blue spot is a person
    http://www.npp.hu/uran/3diff-e.htm
Bomb Material: SSeparating235U by Electromagnetic method
 Bomb Material: eparating 235U by Electromagnetic meth
  Uranium Isotope Enrichment by the
       Electromagnetic Method.               The principle of this
                                             method is the same
                                             as the mass
                                             spectrometry for
                                             chemical analysis.
                                             This is still a very
                                             important method for
                                             chemical analysis
                                             today.
       From a                     238
                                     UF6
       particle       235
                         UF6     collector
       accelerator   collector
Isotope Separation by
Plasma Centrifuge
A vacuum arc produces a plasma column which rotates by action of
an applied magnetic field. The heavier isotopes concentrate in the
outer edge of the plasma column resulting in an enriched mixture
that can be selectively extracted
Nuclear Fusion

Fusion is the process of
 combining two light nuclei to
 form a heavier nucleus

The sun’s energy comes from
 fusion of hydrogen to produce
 helium
Nuclear Fusion (continued)

Releases more energy per gram
 than fission

Requires high temperatures and
 large amounts of energy to
 initiate, but should continue if you
 can get it started
Nuclear Fusion

Fusion
 small nuclei combine

 2H   +    3H           4He   +   1n   +   Energy
  1        1            2         0



 Occurs in the sun and other stars
       Nuclear Fusion in
       Stars

           Stars are giant fusion reactors.
           Nuclear fusion reactions
           provide energy in the Sun and
E = mc2    other stars. Solar energy
 1H, 2D
           drives the weather and makes
 3T, 4He
           plants grow.
           Energy stored in plants
           sustains animal lives, ours
           included.
The Sun
Core:
Radius = 0.25 Rsun
T = 15 Million K
Density = 150 g/cc
Envelope:
Radius = Rsun = 700,000 km
T = 5800 K
Density = 10-7 g/cc
Life of Star:
tug-of-war between Gravity &
Pressure
The
solar
surface
 Nuclear Fusion and Plasma
D and T mixtures have to be
heated to 10 million degrees. At
these temperatures, the mixture is           Plasmas
a plasma.
A plasma is a macroscopically
neutral collection of charged
particles.                                                 Fires
Ions (bare nuclei) at high           Stars
temperature have high kinetic
energy and they approach each
other within 1 fm, a distance                     Neon lights
strong force being effective to
cause fusion.
 Nuclear Fusion and Plasma
 Confinements
                        Three confinement methods




fd3.gif from ippex.pppl.gov/ippex/module_5/see_fsn.html
  Nuclear Fusion using
  Tokamak


      The Tokamak
      technology for
      plasma
      confinement in
      fusion




fd4.gif<=ippex.pppl.gov/ippex/module_5/see_fsn.html
Fusion Research in U.S.A.

 •Princeton Plasma Physics Laboratory (PPPL).
 •Oak Ridge National Laboratory (ORNL).
 •Massachusetts Institute of Technology, Alcator C-
 Mod.
 •University of Wisconsin, HSX.
 •University of Texas, Fusion Research Center.
 •Max Planck Institut fur Plasmaphysik, Wendelstein 7-
 AS
Nuclear Fusion Energised the
Cold War
During WW2, the USSR competed with UK and US for military
superiority. The Cold War started.
Sept. 23, 1949, President Truman told the world about the Soviet
explosion of A-bomb.
The US stepped up to develop the H-bomb.
1952, Nov. 1. US tested the first H-bomb at Enewetak
1953 the USSR tested an H-bomb
Britain, France, and China also have tested H-bombs.
The cold war was red hot until the former USSR disintegrated.
H-bomb



         Nov. 1, 1952, the first H-
         bomb Mike tested,
         mushroom cloud was 8 miles
         across and 27 miles high;the
         canopy was 100 miles wide,
         80 million tons of earth was
         vaporized.
         H-bomb exploded Mar. 1,
         1954 at Bikini Atoll yielded 15
         megatons and had a fireball 4
         miles in diameter.
         USSR H-bomb yields 100
         megatons.
Energy & Nuclear Science
The most important aspect of nuclear
technology is the large amount of
energy involved in nuclear changes,
radioactivity, nuclear reactions,
radiation effects etc.
Thus, the energy concept is very
important before we start to explore
nuclear science.
Nuclear energy associates with mass
according to Einstein’s formula,       E = m c2
        E=mc2
but what does it mean?
Where does the energy come
from?

At the nuclear level, mass and
 energy are interchangeable.
Mass is converted to energy
Energy is converted to mass
Where does the energy come
from?

The mass of a nuclide is less
 than the sum of the masses of its
 constituent parts (protons and
 neutrons
Where does the energy come
from?

Proton = 1.00728 amu
Neutron = 1.00866 amu
Expected mass of 4 He
                  2


2 x 1.00728 + 2 x 1.00866
=4.03188 amu
Where does the energy come
from?

Actual mass of   4
                 2   He
= 4.0026 amu

Difference = 0.02928 amu

Where did this mass go?
Where does the energy come
from?

The difference in the expected mass
 and the actual mass is called the
 “mass defect.”
This mass is converted into the
 energy used to hold the nucleus
 together.
Where does the energy come
from?

Protons are positively charged. If there
  were no force holding them together,
  the protons in the nucleus would repel
  each other.
This force is called the nuclear strong
  force.
The energy used for this force is called
  “binding energy.”
Where does the energy come
from?

              E = mc2

Binding energy = (mass defect) x c2

Note: mass defect must be in kg
(1 amu = 1.66054x10-27 kg)
Where does the energy come
from?

Binding energy for     4
                       2   He
0.02928amu(1.66054 x 10-27 kg/amu)
= 4.86206 x 10-29 kg

E = 4.86206 x 10-29 kg x (2.998x108 m/s)2
= 4.3700x10-12 J
  Estimate Energy in Nuclear
  Reactions

Similarly, the energy in a nuclear reaction is determined based on the
mass difference between the mass of the reactants and the mass of the
products.

  Energy = (mass of products – mass of reactants) x c2


For exothermic reactions (e.g., fission or fusion) the mass of the
products is less than the mass of the reactants. In these reactions, the
mass is converted to energy.
Learning Check NR4

Indicate if each of the following are
(1)Fission     (2) fusion

A.   Nucleus splits                  Energy
B.   Large amounts of energy released
C.   Small nuclei form larger nuclei
D.   Hydrogen nuclei react
Solution NR4

Indicate if each of the following are
(1)Fission     (2) fusion

A. 1     Nucleus splits
B. 1 + 2 Large amounts of energy
   released
C. 2     Small nuclei form larger nuclei
D. 2     Hydrogen nuclei react

				
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